Powered rotary lawn mowers are in wide use by consumers for cutting grass. Such rotary lawn mowers have a housing that encloses a sharpened cutting blade that rotates in a substantially horizontal cutting plane. A handle extends upwardly and rearwardly from the housing to allow an operator to walk behind the housing and to guide the housing during operation of the mower. The housing carries a prime mover, such as an electric motor or internal combustion engine, for rotating the cutting blade. A safety standard that is applicable to consumer lawn mowers requires that the blade come to a stop if the operator releases the handle. In addition, rotation of the blade can be initiated only if the operator performs two distinct actions. Manufacturers of such equipment have offered two major types of mowers that meet these requirements. These mowers comprise zone start mowers and blade brake clutch (BBC) mowers.
In a BBC mower equipped with an internal combustion engine, the engine can be started in a generally conventional manner, using either a rope pull or an electric starter. Once the engine is started, the engine remains running during the operation of the lawn mower unless the engine is purposely shut off by the operator. This is true even if the operator releases the control bail carried on the handle.
In a BBC mower, once the operator releases the control bail, a clutch between the blade and the output shaft of the engine is released and a blade brake is engaged. Thus, even though the engine continues to run, the blade comes to a stop. This can be contrasted with a zone start mower in which the blade comes to a stop once the control bail is released since the engine is killed, i.e. engine ignition is disrupted. Nonetheless, the result is the same in both cases, namely the blade comes to a stop when the operator releases the control bail.
However, in a BBC mower, the control bail must operate differently than in a zone start mower due to the need for two separate operator actions to reengage operation of the blade. In a zone start mower, the first action is the required restarting of the engine. The second action is the closing of the control bail against the crossbar of the handle.
But, in a BBC mower, restarting of the engine cannot be used as the first action since the engine remains running. Thus, the mower must be equipped with some type of additional control that must be actuated before the closure of the control bail is effective to start rotation of the blade. This additional control approach is shown in U.S. Pat. No. 5,784,868 to Wadzinski. Alternatively, the bail can have some type of multi-directional movement before the closure of the control bail places the blade back into operation, as disclosed in U.S. Pat. No. 4,327,539 to Bricko.
The control system used in a BBC mower to start and stop the rotation of the blade is necessarily more complex than that in a zone start mower. Generally speaking, such a BBC control system is not as intuitively obvious to use as that for a zone start mower. Accordingly, there is a need in the art for a BBC control system that is simple and relatively easy to understand and use.